Montana Field Guide

[From Ferris and Brown 1981; Scott 1986; Opler and Wright 1999; Glassberg 2001] Forearm 3.2-3.5 cm. Large. Uppersurface of male unmarked yellow; female orange-yellow to white, forewing with hollow black cell spot, outer margins of both wings edged irregularly with black or black spots. Undersurface yellow-green to warm yellow, males with few markings, females with two large pink-rimmed forewing cell spots and a paler broken postmedian line, hindwing with two central pink-rimmed silver spots.

Many flights; all year in southern Texas and southern Florida, sporadic northward from spring to fall (Scott 1986). Mainly April to October in the West, reaching Colorado by June (Glassberg 2001). June to September in Colorado (Brown 1957; Scott and Scott 1978; Ferris and Brown 1981), May in central and northern California (Shapiro 1993), late May in Oregon (Warren 2005), late June in Montana (Steve Kohler, personal communication).

Best determined by a combination of size, uppersurface solid yellow with few markings, undersurface yellowish with few markings, hindwing of females with two central pink-rimmed silver spots.

Migratory; resident across southeastern US and western Mexico, moves long distances northward, sometimes in large numbers, but does not return southward (Urquhart and Urquhart 1974; Scott 1986; Shapiro 1993; Glassberg 2001; Warren 2005).

Open situations, prairie, weedy fields, irrigated fields, brushy areas, gardens, tropical woodlands, thorn scrub (Ferris and Brown 1981; Scott 1986; Opler and Wright 1999; Glassberg 2001); possibly more abundant in native prairie than restored and disturbed prairie (Debinski and Babbit 1997). Habitat in Montana not described but probably similar.

Larval food plants included exotic and native members of the pea family, particularly Cassia (several species, now under the genus Senna), also Crotalaria and Robinia (Ferris and Brown 1981; Scott 1986, 1992; Graves and Shapiro 2003; Warren 2005). Adults feed on flower nectar (including Abutilon, Alcea, Aloe, Anisacanthus, Antirrhinum, Aquilegia, Aureolaria, Baptisia, Berberis, Bidens, Bougainvillea, Browallia, Buddleja, Calystegia, Campsis, Canna, Cassia, Castilleja, Cercocarpus, Chamaelaucium, Chrysanthemum, Cirsium, Cistus, Clerodendron, Convolvulus, Cordia, Cornus, Crossandra, Cuphea, Delphinium, Dianthus, Digitalis, Dolichandra, Echincea, Encelia, Epilobium, Eupatorium, Euphorbia, Ferocactus, Gaillardia, Geranium, Hamelia, Helianthus, Hibiscus, Impatiens, Ipomoea, Ipomopsis, Ixora, Justicia, Lantana, Liatris, Lobelia, Lonicera, Magnolia, Malvaviscus, Melilotus, Merremia, Mimulus, Mirabilis, Nemesia, Opuntia, Pelargonium, Penstemon, Pentas, Petunia, Phlox, Plumbago, Poinciana, Prunella, Rhaphiolepis, Rhododendron, Rosa, Ruellia, Salvia, Saponaria, Senecia, Senna, Solidago, Stachytarpheta, Symphyotrichum, Tanacetum, Temnadenia, Tithonia, Trifolium, Tropaeolum, Valerianella, Verbena, Veronia, Viola, Watsonia, Zinnia), wet sand, mud, garbage, carrion, and dung (Tooker et al. 2002; Scott 2014).

Females lay eggs singly on young host plant leaves or flower buds (Scott 1986, 1992). Larvae feed on host plant leaves, build no nests. Apparently no stage hibernates or undergoes diapause (Scott 1979, 1986); flies year-round where resident, fails to establish colonies elsewhere over the short term (Ferris and Brown 1981; Scott 1986; Shapiro 1993). Males patrol throughout the day over relatively flat terrain in search of females (Scott 1975b, 1986).